Add support for string to int slice conversion

Signed-off-by: Fabio Falzoi <fabio.falzoi@isovalent.com>

cast_test.go

@@ -648,10 +648,15 @@ func TestToIntSliceE(t *testing.T) {
 		{[]interface{}{1.2, 3.2}, []int{1, 3}, false},
 		{[]string{"2", "3"}, []int{2, 3}, false},
 		{[2]string{"2", "3"}, []int{2, 3}, false},
+		{"", []int{}, false},
+		{"0", []int{0}, false},
+		{"1 2 3", []int{1, 2, 3}, false},
+		{"-1 -2 -3", []int{-1, -2, -3}, false},
 		// errors
 		{nil, nil, true},
 		{testing.T{}, nil, true},
 		{[]string{"foo", "bar"}, nil, true},
+		{"1 foo 2", nil, true},
 	}
 
 	for i, test := range tests {

caste.go

@@ -1299,6 +1299,17 @@ func ToIntSliceE(i interface{}) ([]int, error) {
 	switch v := i.(type) {
 	case []int:
 		return v, nil
+	case string:
+		ss := strings.Fields(v)
+		a := make([]int, 0, len(ss))
+		for _, s := range ss {
+			v, err := strconv.Atoi(s)
+			if err != nil {
+				return []int{}, fmt.Errorf("unable to cast %#v of type %T to []int", i, i)
+			}
+			a = append(a, v)
+		}
+		return a, nil
 	}
 
 	kind := reflect.TypeOf(i).Kind()